Organization of nervous tissue & Electrical signals

Question 1

Gray matter

Answer 1

Groups of neuron cell bodies and their dendrits, with very little myelin

Question 2

Cortex

Answer 2

Gray matter on the surface of the brain

Question 3

Nuclei

Answer 3

gray matter located deeper within the brain

Question 4

ganglion

Answer 4

Clusters of neuron cell bodies that form gray matter in PNS

Question 5

White matter

Answer 5

bundles of parallel myelinated axons

Question 6

Nerve tracts

Answer 6

White matter of the CNS that propegate action potentials from one area of CNS to another

Question 7

Action potentials

Answer 7

Electrical signals produced by specialized cells

Action potentials are how cells communicate with other cells

Question 8

Electrical properties of cells (2)

Answer 8

1. Ionic concentration differs across the plasma membrane

2. Permeability characteristics differ across the plasma membrane

Question 9

What is the purpose of the sodium potassium pump in a neuron?

Answer 9

maintains high concentraion of K+ in the cytoplasm and high concentration of Na+ in the extracellular fluid.

Uses ATP to make the sodium-potassium pump work

Question 10

Ion channels (4)

Answer 10

Leak ion channels (always open)
Ligand-gated - opened by binding a specific molecule to the recptor site of the ion channel
VOltage-gated - open and close in response to specific, small voltage change across plasma membrane
Other ion gated

Question 11

Opposite charges between the inside of the cell and the extracellular fluid results in -

Answer 11

polarization

Question 12

Potential difference

Answer 12

Electrical charge difference across the plasma membrane

Question 13

Resting membrane potential

Answer 13

The potential difference in an unstimulated, resting cell

Question 14

When is resting membrane potential equilibrium established

Answer 14

When tendancy for K+ to diffuce out o the cell is equal to tendency for K+ to move in to the cell

Question 15

Which ions most influence resting potential?

Answer 15

K+

Question 16

Which ions have minor influence on resting potential?

Answer 16

Na+, Cl-, and Ca2+

Question 17

Depolarization

Answer 17

Occurs when teh membrane potential becomes more positive; membrane potential moves closer to zero

Question 18

Hyperpolarization

Answer 18

occurs when teh membrane potential becomes more negative; membrane potential moves further away from zero

Question 19

Hypokalemia

Answer 19

Lower-than-normal concentraion of K+ in teh blood or extracellular fluid > hyperpolarizes resting membrane potential

Causes excitable tissues to become less sensitive to stimulation > muscular weakness, abnormal electrocardiogram, sluggish reflexes

Caused by depletion of potassium during starvation, alkalosis, or certain kidney diseases

Question 20

Hypocalcemia

Answer 20

lower-than-normal concentration of Ca2+ in the blood or extracellular fluid

Nervousness and uncontrolled contraction of skeletal muscles (tetany)

Caused by lack of dietary calcium or vitamin D

Question 21

Graded potential

Answer 21

relatively small change in teh membrane potential that is localized to one area of the plasma membrane

Often leads to action potentials

Question 22

Summation

Answer 22

effects of one graded potential combine with effects of a different grade potential elsewhere on plasma membrane

Question 23

Threshold

Answer 23

The limite at which graded potentials must summat to trigger an action potential

It’s when voltage-gated Na+ channels open

Question 24

Where do action potentials initiate?

Answer 24

Action potentials occur at the trigger zone because there is a higher proportion of voltage-gated channels there than other parts of the cell body

Question 25

Phases of the action potential

Answer 25

Depolarization (becomes more positive) Repolarization (become more negative) Afterpotential (short period of hyperpolarization)

Question 26

All or none principle

Answer 26

stimulus is large enough to reach the threshold, an action potential occurs. If a stimulus is too weak, for depolarizing graded potential to not meet the threshold, there is no action potential produced.

Question 27

Refractory period

Answer 27

The time period when an action potential causes an area to become less sensitive to further stimulation

Question 28

Absolute refractory period

Answer 28

the first part of the refractory period where complete insensitivity to another stimulus exists.

Question 29

Relative refractory period

Answer 29

A very strong stimulus can initiate another action potential during the relative refractor period

Question 30

Propagation of Action potentials

Answer 30

Like dominoes - each domino triggers the next domino to topple

Question 31

Local current

Answer 31

movement of positively charged ions

Question 32

Continuous conduction

Answer 32

Action potential that occurs in unmyelinated axons The local current causes the membrane adjacent to the action potential to depolarize > depolarization reaches threshold > produces further action potential

Question 33

Saltatory conduction

Answer 33

Action potential conducted in myelinated axons from one node of Ranvier to another

Question 34

What determines the speed of an action potential? (2)

Answer 34

The thickness of the myeline sheath. Cells with more oligodendrocytes or Schwann cells conduct action potentially more rapidly. Diameter of an axon > the larger, the more rapidly the action potential will be conducted

Question 35

Types of nerve fibers (3)

Answer 35

Type A Type B Type C

Question 36

Type A fibers

Answer 36

large diameter, myelinated axons that conduct rapid action potentials Motor neurons supplying skeletal muscle and sensory neurons

Question 37

Type B fibers

Answer 37

medium diameter, lightly myelinated axons Part of ANS - signals internal organs and responses necessary to maintain homeostasis

Question 38

Type C fibers

Answer 38

small diameter, unmyelinated axons Part of ANS - signals internal organs and responses necessary to maintain homeostasis